/*
 * Copyright (c) 2005, 2006, Oracle and/or its affiliates. All rights reserved.
 * DO NOT ALTER OR REMOVE COPYRIGHT NOTICES OR THIS FILE HEADER.
 *
 * This code is free software; you can redistribute it and/or modify it
 * under the terms of the GNU General Public License version 2 only, as
 * published by the Free Software Foundation.  Oracle designates this
 * particular file as subject to the "Classpath" exception as provided
 * by Oracle in the LICENSE file that accompanied this code.
 *
 * This code is distributed in the hope that it will be useful, but WITHOUT
 * ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or
 * FITNESS FOR A PARTICULAR PURPOSE.  See the GNU General Public License
 * version 2 for more details (a copy is included in the LICENSE file that
 * accompanied this code).
 *
 * You should have received a copy of the GNU General Public License version
 * 2 along with this work; if not, write to the Free Software Foundation,
 * Inc., 51 Franklin St, Fifth Floor, Boston, MA 02110-1301 USA.
 *
 * Please contact Oracle, 500 Oracle Parkway, Redwood Shores, CA 94065 USA
 * or visit www.oracle.com if you need additional information or have any
 * questions.
 */

package com.sun.tools.javac.model;

import java.util.EnumSet;
import java.util.List;
import java.util.Set;

import javax.lang.model.element.Element;
import javax.lang.model.element.TypeElement;
import javax.lang.model.type.ArrayType;
import javax.lang.model.type.DeclaredType;
import javax.lang.model.type.ExecutableType;
import javax.lang.model.type.NoType;
import javax.lang.model.type.NullType;
import javax.lang.model.type.PrimitiveType;
import javax.lang.model.type.ReferenceType;
import javax.lang.model.type.TypeKind;
import javax.lang.model.type.TypeMirror;
import javax.lang.model.type.WildcardType;

import com.sun.tools.javac.code.BoundKind;
import com.sun.tools.javac.code.Symbol;
import com.sun.tools.javac.code.Symbol.ClassSymbol;
import com.sun.tools.javac.code.Symtab;
import com.sun.tools.javac.code.Type;
import com.sun.tools.javac.code.TypeTags;
import com.sun.tools.javac.code.Types;
import com.sun.tools.javac.util.Context;
import com.sun.tools.javac.util.ListBuffer;

/**
 * Utility methods for operating on types.
 * 
 * <p>
 * <b>This is NOT part of any supported API. If you write code that depends on
 * this, you do so at your own risk. This code and its internal interfaces are
 * subject to change or deletion without notice.</b>
 * </p>
 */
public class JavacTypes implements javax.lang.model.util.Types {

	private Symtab syms;
	private Types types;

	private static final Context.Key<JavacTypes> KEY = new Context.Key<JavacTypes>();

	public static JavacTypes instance(Context context) {
		JavacTypes instance = context.get(KEY);
		if (instance == null) {
			instance = new JavacTypes(context);
			context.put(KEY, instance);
		}
		return instance;
	}

	/**
	 * Public for use only by JavacProcessingEnvironment
	 */
	// TODO JavacTypes constructor should be protected
	public JavacTypes(Context context) {
		setContext(context);
	}

	/**
	 * Use a new context. May be called from outside to update internal state
	 * for a new annotation-processing round. This instance is *not* then
	 * registered with the new context.
	 */
	public void setContext(Context context) {
		syms = Symtab.instance(context);
		types = Types.instance(context);
	}

	public Element asElement(TypeMirror t) {
		Type type = cast(Type.class, t);
		if (type.tag != TypeTags.CLASS && type.tag != TypeTags.TYPEVAR)
			return null;
		return type.asElement();
	}

	public boolean isSameType(TypeMirror t1, TypeMirror t2) {
		return types.isSameType((Type) t1, (Type) t2);
	}

	public boolean isSubtype(TypeMirror t1, TypeMirror t2) {
		validateTypeNotIn(t1, EXEC_OR_PKG);
		validateTypeNotIn(t2, EXEC_OR_PKG);
		return types.isSubtype((Type) t1, (Type) t2);
	}

	public boolean isAssignable(TypeMirror t1, TypeMirror t2) {
		validateTypeNotIn(t1, EXEC_OR_PKG);
		validateTypeNotIn(t2, EXEC_OR_PKG);
		return types.isAssignable((Type) t1, (Type) t2);
	}

	public boolean contains(TypeMirror t1, TypeMirror t2) {
		validateTypeNotIn(t1, EXEC_OR_PKG);
		validateTypeNotIn(t2, EXEC_OR_PKG);
		return ((Type) t1).contains((Type) t2);
	}

	public boolean isSubsignature(ExecutableType m1, ExecutableType m2) {
		return types.isSubSignature((Type) m1, (Type) m2);
	}

	public List<Type> directSupertypes(TypeMirror t) {
		validateTypeNotIn(t, EXEC_OR_PKG);
		Type type = (Type) t;
		Type sup = types.supertype(type);
		return (sup == Type.noType || sup == type || sup == null) ? types
				.interfaces(type) : types.interfaces(type).prepend(sup);
	}

	public TypeMirror erasure(TypeMirror t) {
		if (t.getKind() == TypeKind.PACKAGE)
			throw new IllegalArgumentException(t.toString());
		return types.erasure((Type) t);
	}

	public TypeElement boxedClass(PrimitiveType p) {
		return types.boxedClass((Type) p);
	}

	public PrimitiveType unboxedType(TypeMirror t) {
		if (t.getKind() != TypeKind.DECLARED)
			throw new IllegalArgumentException(t.toString());
		Type unboxed = types.unboxedType((Type) t);
		if (!unboxed.isPrimitive()) // only true primitives, not void
			throw new IllegalArgumentException(t.toString());
		return unboxed;
	}

	public TypeMirror capture(TypeMirror t) {
		validateTypeNotIn(t, EXEC_OR_PKG);
		return types.capture((Type) t);
	}

	public PrimitiveType getPrimitiveType(TypeKind kind) {
		switch (kind) {
		case BOOLEAN:
			return syms.booleanType;
		case BYTE:
			return syms.byteType;
		case SHORT:
			return syms.shortType;
		case INT:
			return syms.intType;
		case LONG:
			return syms.longType;
		case CHAR:
			return syms.charType;
		case FLOAT:
			return syms.floatType;
		case DOUBLE:
			return syms.doubleType;
		default:
			throw new IllegalArgumentException("Not a primitive type: " + kind);
		}
	}

	public NullType getNullType() {
		return (NullType) syms.botType;
	}

	public NoType getNoType(TypeKind kind) {
		switch (kind) {
		case VOID:
			return syms.voidType;
		case NONE:
			return Type.noType;
		default:
			throw new IllegalArgumentException(kind.toString());
		}
	}

	@SuppressWarnings("incomplete-switch")
	public ArrayType getArrayType(TypeMirror componentType) {
		switch (componentType.getKind()) {
		case VOID:
		case EXECUTABLE:
		case WILDCARD: // heh!
		case PACKAGE:
			throw new IllegalArgumentException(componentType.toString());
		}
		return new Type.ArrayType((Type) componentType, syms.arrayClass);
	}

	public WildcardType getWildcardType(TypeMirror extendsBound,
			TypeMirror superBound) {
		BoundKind bkind;
		Type bound;
		if (extendsBound == null && superBound == null) {
			bkind = BoundKind.UNBOUND;
			bound = syms.objectType;
		} else if (superBound == null) {
			bkind = BoundKind.EXTENDS;
			bound = (Type) extendsBound;
		} else if (extendsBound == null) {
			bkind = BoundKind.SUPER;
			bound = (Type) superBound;
		} else {
			throw new IllegalArgumentException(
					"Extends and super bounds cannot both be provided");
		}
		switch (bound.getKind()) {
		case ARRAY:
		case DECLARED:
		case ERROR:
		case TYPEVAR:
			return new Type.WildcardType(bound, bkind, syms.boundClass);
		default:
			throw new IllegalArgumentException(bound.toString());
		}
	}

	public DeclaredType getDeclaredType(TypeElement typeElem,
			TypeMirror... typeArgs) {
		ClassSymbol sym = (ClassSymbol) typeElem;

		if (typeArgs.length == 0)
			return (DeclaredType) sym.erasure(types);
		if (sym.type.getEnclosingType().isParameterized())
			throw new IllegalArgumentException(sym.toString());

		return getDeclaredType0(sym.type.getEnclosingType(), sym, typeArgs);
	}

	public DeclaredType getDeclaredType(DeclaredType enclosing,
			TypeElement typeElem, TypeMirror... typeArgs) {
		if (enclosing == null)
			return getDeclaredType(typeElem, typeArgs);

		ClassSymbol sym = (ClassSymbol) typeElem;
		Type outer = (Type) enclosing;

		if (outer.tsym != sym.owner.enclClass())
			throw new IllegalArgumentException(enclosing.toString());
		if (!outer.isParameterized())
			return getDeclaredType(typeElem, typeArgs);

		return getDeclaredType0(outer, sym, typeArgs);
	}

	// where
	private DeclaredType getDeclaredType0(Type outer, ClassSymbol sym,
			TypeMirror... typeArgs) {
		if (typeArgs.length != sym.type.getTypeArguments().length())
			throw new IllegalArgumentException(
					"Incorrect number of type arguments");

		ListBuffer<Type> targs = new ListBuffer<Type>();
		for (TypeMirror t : typeArgs) {
			if (!(t instanceof ReferenceType || t instanceof WildcardType))
				throw new IllegalArgumentException(t.toString());
			targs.append((Type) t);
		}
		// TODO: Would like a way to check that type args match formals.

		return (DeclaredType) new Type.ClassType(outer, targs.toList(), sym);
	}

	/**
	 * Returns the type of an element when that element is viewed as a member
	 * of, or otherwise directly contained by, a given type. For example, when
	 * viewed as a member of the parameterized type {@code Set<String>}, the
	 * {@code Set.add} method is an {@code ExecutableType} whose parameter is of
	 * type {@code String}.
	 * 
	 * @param containing
	 *            the containing type
	 * @param element
	 *            the element
	 * @return the type of the element as viewed from the containing type
	 * @throws IllegalArgumentException
	 *             if the element is not a valid one for the given type
	 */
	public TypeMirror asMemberOf(DeclaredType containing, Element element) {
		Type site = (Type) containing;
		Symbol sym = (Symbol) element;
		if (types.asSuper(site, sym.getEnclosingElement()) == null)
			throw new IllegalArgumentException(sym + "@" + site);
		return types.memberType(site, sym);
	}

	private static final Set<TypeKind> EXEC_OR_PKG = EnumSet.of(
			TypeKind.EXECUTABLE, TypeKind.PACKAGE);

	/**
	 * Throws an IllegalArgumentException if a type's kind is one of a set.
	 */
	private void validateTypeNotIn(TypeMirror t, Set<TypeKind> invalidKinds) {
		if (invalidKinds.contains(t.getKind()))
			throw new IllegalArgumentException(t.toString());
	}

	/**
	 * Returns an object cast to the specified type.
	 * 
	 * @throws NullPointerException
	 *             if the object is {@code null}
	 * @throws IllegalArgumentException
	 *             if the object is of the wrong type
	 */
	private static <T> T cast(Class<T> clazz, Object o) {
		if (!clazz.isInstance(o))
			throw new IllegalArgumentException(o.toString());
		return clazz.cast(o);
	}
}
